1. Field of the Invention
The present invention relates generally to oxygen Reactive Ion Etch (RIE) plasma methods for removing organic residues from semiconductor substrates. More particularly, the present invention relates to an improved oxygen Reactive Ion Etch (RIE) plasma method which includes non-explosive hydrogen containing species within the plasma, which improved oxygen plasma method is useful in removing from semiconductor substrates oxidized organic residues such as oxidized photoresist residues.
2. Description of the Background Art
Advanced semiconductor integrated circuit device chips are typically manufactured through processes which provide multiple conductive layers and multiple insulating layers upon a plurality of active semiconductor substrate regions. These layers and regions are typically defined and formed through etching and masking processes which involve the photolithographic exposure and developing of blanket photoresist layers. Commonly, a photolithographically exposed blanket photoresist layer will be developed into a patterned photoresist layer through which features to be formed within or upon a semiconductor substrate are defined.
Subsequent to photolithographic exposure and development, patterned photoresist layers which remain upon a semiconductor substrate may be exposed to semiconductor manufacturing processes which significantly alter the chemical or physical structure of those patterned photoresist layers. Such manufacturing processes may include: (1) implanting of high doses of dopant species into those patterned photoresist layers, (2) exposure of those patterned photoresist layers to substantial quantities of radiative energy, or (3) exposure of those patterned photoresist layers to elevated temperatures. Each of these manufacturing processes may produce changes in patterned photoresist layers which yield substantial concentrations of oxidized species within those patterned photoresist layers.
Typically, patterned photoresist layers are removed prior to forming over-lying layers of the semiconductor structure within which those patterned photoresist layers were formed. Commonly, patterned photoresist layers are removed from the semiconductor substrates upon which they were formed through exposure of the patterned photoresist layers to an oxygen Reactive Ion Etch (RIE) plasma. However, patterned photoresist layers which contain substantial quantities of oxidized species may be difficult to remove from semiconductor substrates through oxygen Reactive Ion Etch (RIE) plasma processes since oxidized species within patterned photoresist layers are often unaffected by the chemical and physical effects of oxygen Reactive Ion Etch (RIE) plasmas.
Thus, it is often necessary to include into such oxygen Reactive Ion Etch (RIE) plasmas a reducing material which may react effectively with the oxidized species contained within the oxidized patterned photoresist layer. The most common reducing material which may be incorporated into an oxygen Reactive Ion Etch (RIE) plasma to assist in removal of oxidized species within patterned photoresist layers is hydrogen gas. Hydrogen gas is typically incorporated into those oxygen Reactive Ion Etch (RIE) plasmas in the form of forming gas mixtures such as nitrogen/hydrogen mixtures and helium/hydrogen mixtures.
While oxygen Reactive Ion Etch (RIE) processes which contain reducing materials such as hydrogen gas are usually quite effective in removing oxidized organic residues such as oxidized photoresist residues from semiconductor substrates, such Reactive Ion Etch (RIE) plasmas are not without problems. In particular hydrogen gas containing reducing materials when used within oxygen Reactive Ion Etch (RIE) plasmas are typically expensive in comparison with other materials used within those Reactive Ion Etch (RIE) plasmas. In addition, hydrogen gas mixtures when provided into an oxygen Reactive Ion Etch (RIE) plasma also possess an inherent safety concern related to the explosive characteristics of hydrogen gas in ambient atmospheres containing oxygen.
Therefore, although it is desirable to provide an oxygen Reactive Ion Etch (RIE) plasma containing a sufficient quantity of reducing material to effectively remove oxidized organic residues such as oxidized photoresist residues from semiconductor substrates, it is also desirable that the reducing material incorporated into that oxygen Reactive Ion Etch (RIE) plasma provide a plasma which is both economical and safe to use in a manufacturing environment. It is towards these two goals that the present invention is directed.